Java:是否有可能排除从父类(super class)中获取某些东西

Question

我正在处理一项处理类继承的作业，除了字符串格式方法外，一切都已完成并正常工作。该程序的输出应如下所示:

Base Salary Plus Commissioned Employee: Sue Smith with ssn: 222-22-2222
Gross Sales: $3000.00 
Commission Rate: 0.05 
with Base Salary:$300.00 
Earnings: $450.00

但是它是这样打印的:

Base Salary Plus Commissioned Employee: Sue Smith with ssn: 222-22-2222
Gross Sales: $3000.00 
Commission Rate: 0.05 
Earnings: $450.00
with Base Salary:$300.00 
Earnings: $450.00

问题是在输出中，“Earnings: $450.00”打印在“with Base Salary: $300.00”之前。 BasePlusCommissionEmployee 类继承自 CommissionEmployee 类。每个类都有自己的 toString 方法，BasePlusCommissionEmployee 确实调用了 super.toString()，我认为这是导致问题的原因。

我需要能够让类从 CommissionEmployee 继承，但直到最后才带来“ yield ”(如图所示)。

这是 CommissionEmployee 类中 toString 的代码:

    @Override
    public String toString() {                                    
        return String.format("%s: %s%n%s: $%.2f \n%s: %.2f \n%s $%.2f",    
         "Commissioned Employee", super.toString(),              
         "Gross Sales", getGrossSales(),                       
         "Commission Rate", getCommissionRate(), 
         "Earnings:", earnings());             
   }  

这是 BasePlusCommissionEmployee 类(从 CommissionEmployee 扩展)中的 toString 代码:

    @Override
    public String toString() {                                            
        return String.format("\n%s %s \n%s:$%,.2f \n%s $%.2f",                       
            "Base Salary Plus", super.toString(),                            
            "with Base Salary", getBaseSalary(),
            "Earnings:",earnings());                             
   }  

这是在main中运行的测试代码:

CommissionEmployee employee1 = new CommissionEmployee("Fred", "Jones", "111-11-1111", 2000.0, .05);
BasePlusCommissionEmployee employee2 = new BasePlusCommissionEmployee("Sue", "Smith", "222-22-2222", 3000.0, .05, 300);
System.out.printf("%s%s%s%s%s", employee1, employee2, employee3, employee4, employee5);

非常感谢所有帮助!谢谢!

Answer 1

本书的第一章几乎解决了这个问题 Refactoring由 Martin Fowler 撰写，“分解和重新分配声明方法”部分。 toString()方法在基类中可以分解如下:

    @Override
    public String toString() {
        return getReportHeader() 
                + getReportBase() 
                + getReportSpecifics() 
                + getReportFooter();
    }

    protected String getReportHeader() {
        return String.format("%s: %s",
                             "Commissioned Employee", super.toString());
    }

    protected String getReportBase() {
        return String.format("\n%s %s \n%s:$%,.2f",
                             "Gross Sales", getGrossSales(),
                             "Commission Rate", getCommissionRate());
    }

    protected String getReportSpecifics() {
        return "";
    }

    protected String getReportFooter() {
        return String.format("\n%s $%.2f", "Earnings:", earnings());
    }

然后可以在子类中覆盖所需的部分:

    @Override
    protected String getReportSpecifics() {
        return String.format("\n%s %s \n%s:$%,.2f",
                             "Base Salary Plus", getBaseSalaryPlus(),
                             "with Base Salary", getBaseSalary());
    }

不过，我建议您阅读整本书。它物有所值。